The present invention relates to a thermal cycler for use in carrying out controlled heating and cooling of biological samples, for example DNA strands.
Traditionally, scientists have used the technique of the Polymerase Chain Reaction (PCR) to synthesize defined sequences of DNA. This generally involves a three step procedure: separation of the DNA to be amplified (template DNA); annealing of short complimentary DNA sequences (primers) to the template DNA and finally the addition of deoxynucleotides to the primer strands in order to copy the template DNA. This is usually performed in a thermal cycling machine where a cycle of three different temperatures is repeated approximately 25-35 times. Template DNA separation and synthesis steps occur at defined temperatures. However, the temperature at which the primer binds to the DNA, may need optimizing in order for this step to occur efficiently and achieve desirable PCR results. Primer annealing optimization experiments usually involve setting up a number of different experiments where only the primer annealing temperature is varied. The experiment may need to be performed 3 or 4 times in order to determine the optimum binding temperature. These experiments would have to be repeated each time a new set of primers was required for different PCRs. The development of a temperature gradient block enables the scientists to determine the optimum binding temperatures of several primer sets in a single experiment.
However, prior art derives which produce a thermal gradient have been relatively complex and expensive.
The present invention seeks to provide an improved thermal cycler.
According to an aspect of the present invention, there is provided a thermal cycler including a sample plate able to hold a plurality of samples, a plurality of heating and cooling elements located along the sampling plate, supply means operable to provide a current to the heating and cooling elements, and switching means able to switch current individually through each heating or cooling element or each of a plurality of sets of heating or cooling elements.
The temperature gradient block can achieve a set of discrete temperatures simultaneously, thereby decreasing the number of optimization experiments the scientist needs to perform and therefore the workload.